In many electric submersible pump (ESP) operations, deep set packers are required to protect casing annulus from contact with reservoir fluid and as a barrier for well control. In these cases, the ESP is located below the packer, which requires a packer penetrator system to be used to connect the ESP's electrical power cable above the packer to the motor lead cable below. In these applications, the penetrator system and the lower motor lead cable can represent a major failure mode for the ESP. Often, a high percentage of failures are directly related to the packer penetrator, motor lead cable, or motor pot head. Additionally, as the packer above the ESP creates a pressure boundary in the annulus, ESP's can not produce with pump intake pressures below the fluid bubble point pressure without creating gas pockets below the packer. This phenomenon often causes operators to reduce production rates from a well as draw downs are restricted to maintain certain pump intake pressures.
An alternative to the conventional packer/ESP installation discussed above is to modify the completion to incorporate the packer below the ESP, thus maintaining the integrity of the casing profile. Because the packer is located below the ESP, the ESP is run inside a concentric encapsulated shroud. The shroud is connected to a shroud hanger, which is connected to production tubing above the pump discharge head of the ESP. The shroud is ultimately connected to a tailpipe/stinger which is inserted into the packer below. This allows reservoir fluid from below the packer to flow through the tailpipe/stinger assembly and into the shrouded ESP. The shroud isolates the casing above the packer from contact with the reservoir fluid, thereby ensuring the integrity of the casing. The ESP power cable is connected to a penetrator system that passes through the shroud hanger and connects to the motor lead cable below. The motor lead cable is connected to the motor at the motor's pot head, thereby providing the electrical power for the ESP. This design requires a penetrator system through the shroud, similar to those required for packers, and it further requires that the penetrator either be spliced to the motor lead cable or be factory molded to the motor lead cable within the shroud. As such, the potential for penetrator failure noted above still exists. Additionally, in this particular design, due to the location of the shroud hanger relative to the pump intake, a pocket of gas may accumulate within the shroud. As a result, pump intake pressures at or below bubble point pressures are not desirable.
A need exists for a technique that reduces ESP assembly failures associated with cable penetrator systems and motor lead cables. Additionally, a need exists for a technique that allows an ESP to produce at or below bubble point pressures when deep set packers are required. The following technique may solve one or more of these problems.